The present invention relates to an elastic buffer for use in a local area network system so that a station in the network which reclocks data and establishes the frequency standard can absorb frequency jitter caused by data acquisition in the other stations of the network.
In a local area network system utilizing ring topology where a self-clocking data scheme is used it is necessary for at least one station to reclock the data and establish the frequency standard for the ring. However, before doing so it is necessary for that station to first absorb the frequency jitter caused by other stations in the system. One way of absorbing this jitter is to use an elastic buffer having a `FIRST IN FIRST OUT` or FIFO stack together with associated circuitry to control data flow into and out of the stack. Data would be clocked into the buffer on a clock frequency derived from the incoming signal itself and clocked out on a crystal clock of a fixed frequency. Whenever the phase difference between incoming and outgoing data exceeds a predetermined amount an error signal would be recorded and the FIFO reset to its nominal center position. Such a buffer would have to be capable of operating at very high frequencies of several megabits per second and also be capable of reliably recording errors without corrupting the data. The stack must be large enough to deal with normal levels of frequency jitter and be able to record errors and reset the FIFO in response to such errors. Accordingly, it is an object of the present invention to provide an elastic buffer for a local area network system to absorb frequency jitter caused by other stations on the network handling the data.